Carbohydrates are seen by many as ‘the enemy’ of healthy body weight. The mantra ‘no carbs before Marbs’ (from TV’s The Only Way Is Essex – about holidaying in Marbella) reflects a widespread view that carbs lead to fat gain.
This is based on the fact that carbohydrates – such as bread, potatoes, pasta, cakes and biscuits – are broken down into glucose in the body – which can raise blood sugar levels; over time, this can lead to weight gain and health problems, such as type 2 diabetes and heart disease.
But has our understanding of this been wrong?
A study, published in the journal Cell Metabolism, suggests that in some people it’s actually fat and protein, rather than carbs, that cause high blood sugar. Levels are generally kept in check by insulin, a hormone produced by beta cells in the pancreas that helps cells mop up glucose and use it for energy.
Insulin also assists the body in storing extra glucose in the form of glycogen, mainly in the muscles and liver (it’s then returned to the blood when blood sugar levels are too low).
Testing blood sugar levels at home with a glucometer is often carried out by people with, or at risk of, diabetes
But if the cells stop responding to insulin, excess glucose circulates in the bloodstream.
The pancreas then pumps out more and more insulin to keep blood sugar down – until it can’t keep up, causing type 2 diabetes. Over time high blood sugar levels damage blood vessels and nerves.
In the latest study, scientists at the University of British Columbia in Canada took 140 pancreatic islets (clusters of pancreatic cells including beta cells) from deceased human donors with and without type 2 diabetes.
They also took pancreatic islets made from stem cells (‘master’ cells that can form different types of cells in the body). The experts then looked at how much insulin these secreted in response to carbohydrates, proteins and fats.
The study showed – for the first time – that some human pancreatic islets made more insulin in response to fatty acids (fats) and amino acids (protein) compared with glucose (carbohydrates). This turned traditional thinking on its head.
So could this change the advice given to some people?
‘It’s an interesting concept and it can offer some explanation for the variability we see in terms of how responsive people are to specific diets – for instance, to low-carb diets – so we know there’s no one measure that fits all,’ says Dr Efthimia Karra, a consultant endocrinologist at the Royal Free Hospital and Princess Grace Hospital, both in London.
Aisling Pigott, a dietitian with a special interest in diabetes for NHS Wales, says: ‘In clinic, we see [from glucose monitors] that some people experience a rise in glucose from carbohydrates and others can respond more to protein and fat. It depends on the individual and the quantity that they’ve eaten.’
No carbs before Marbs was the mantra of some of the stars on TV show The Only Way Is Essex
The study results, she says, are confirmation that no two people are the same in terms of how they respond to food and that metabolism is complex.
‘It could help take away the blame and frustration that some people with diabetes feel when they are working hard but failing to lose weight and improve their blood sugar levels,’ she adds.
A high-fat diet might not necessarily be the answer, as it can lead to fat accumulating around the abdomen. This kind of fat increases inflammation in the body, which is thought to make cells less responsive to insulin.
This latest research has implications for countries such as the UK, where our diet tends to be carbohydrate heavy, adds Roy Taylor, a professor of medicine and metabolism at Newcastle University, who helped develop a low-calorie diet that’s been shown to put type 2 diabetes into remission.
It involves having meal replacement soups and shakes for the first 12 weeks (totalling between 800 and 900 calories each day).
Professor Taylor says there is a place for carbs in our diet but it’s the added calories from them that is the problem. ‘It’s so easy to overeat a pile of mashed potatoes or consume excess pasta or rice,’ he adds.
Additionally, having too many carbohydrates can trigger different responses in the body, depending on how sensitive you are to insulin, explains Professor Taylor. ‘If you have normal insulin sensitivity, then your breakfast cornflakes are heading towards your muscle glycogen stores, but if you don’t, then the body immediately transfers much of that glucose into fat.’
Everyone has different sensitivity to insulin, dictated by genes.
It may not be obvious if you are insulin resistant so it’s worth looking at your family history. If a relative has had a heart attack or diabetes then consider cutting back on the carbohydrates, says Professor Taylor.
This is because if you’re insulin resistant and excess carbohydrates are stored as fat, then it can lead to clogged up arteries, increasing the risk of heart attack or stroke.
Professor Roy Taylor says it may not be obvious that you are insulin resistant
But this can be modified to a small extent by regular exercise and weight gain or loss.
Other factors, such as ageing and hormonal changes, can affect our response to foods, adds Aisling Pigott, who is also a spokeswoman for the British Dietetic Association.
‘For example, when women are perimenopausal and menopausal, their level of oestrogen drops, which affects their muscle maintenance so they may have a higher percentage of body fat than before, and we know that this increases resistance to insulin.’
Similarly, the stress hormone cortisol can stop insulin working as well as it should.
When it comes to the latest research the experts agree more studies are needed to find if this translates into people. As Professor Taylor says: ‘It’s important to note that some of the results of the study related to the length of the time the islets were in culture in the lab [the longer they were in the lab, the more time they had to secrete insulin, meaning higher amounts] – it’s so far from the situation in real, living people.
‘Type 2 diabetes is a crushingly simple disease – people heading towards diabetes have usually become too heavy for their own body,’ he adds.
‘Bear in mind that any weight gain in adult life is all fat – we don’t naturally grow extra muscle, bone or brain tissue so people’s weight in middle age should really be what they were when they were 20.’
His views resonate with Dr Karra: ‘Ultimately, the key message remains to keep your weight within healthy levels and that there may need to be an element of trial and error to find the best diet that achieves this for you.’
And in the short-term, there’s a simple but key bit of advice. As Aisling Pigott explains: ‘It’s essential to be active within an hour of consuming a meal.
‘This can massively reduce the post-meal rise in glucose levels because when we move, our cells absorb glucose for energy, and it increases the impact of the insulin we have, in turn reducing our cells’ resistance to it.’
She adds: ‘This doesn’t have to mean going to the gym – a gentle walk, or just tidying the kitchen can help – but it really is helpful to avoid being stationary around this time.’
[Notigroup Newsroom in collaboration with other media outlets, with information from the following sources]
